Depends on the position on the line. The interactive chart here [1] shows that concussions by position for one year. Tackles have a much higher incidence than the center, the guards or the defensive linemen. Wide receivers, running backs, the defensive secondary and linebackers have a lot more though. The guys on the line have so many more reps in games and in practices that the damage is of more of a chronic nature.
Ah, very interesting. I wouldn't have guessed that tackles (11) have almost twice the risk of guards (6) -- maybe they tend to get farther downfield on run plays? I looked through the 11 tackle concussions listed, and only one said what type of play it was (a run play); another one was from being kneed in the head.
Centers (3), OTOH, have by this estimate about half the risk of guards (6). This guy should move to center. That's where you want someone really smart anyway as centers have to set up blocking assignments at the line. Also I see the scouting report recommended him for center based on his body type and playing style.
[1] http://www.pbs.org/wgbh/pages/frontline/concussion-watch/#po...